I'm guessing you mean how to cut down the whole pork shoulder? A meat cutter is likely going to use a meat saw. I assume you don't have one of those, so if I were in your situation, I'd be tempted to bone the whole thing out.
Assuming you have a nice sharp knife, start at the hock or small end (is there a round bone?), then simply follow the leg bone up the shoulder. You may get to a joint, which will tie into a blade bone which exists at the top. It will look like a real mess. BUTT (pun intended), when you have the bones out, pull it all back together and tie it in a bundle with some cotton twine (not nylon or some synthetic, but cotton). You can then leave that entire piece whole, or block it into two pieces. Won't be the same as the pretty stuff you see on the forum, but you have a handicap we don't.